The present invention relates to adjustable, hospital-type beds, and in particular to a hinge therefor.
Adjustable beds, such as those disclosed in U.S. Pat. Nos. 3,919,727; 3,414,913; 3,281,872; and 3,281,873, which are hereby incorporated by reference, are used in hospitals, nursing homes, and other similar institutions, particularly for the care of nonambulatory patients. Such adjustable beds usually have a head section, a seat or center section, and a foot section, which are pivotally supported on a frame. The three bed sections are adjustable to provide patient comfort, as well as a wide range of therapeutic positions.
One problem experienced with such adjustable beds is that the mattress tends to bend and compress along the hinge axis of the bed when the bed sections are rotated from a flat to a raised position. This condition is particularly pronounced at the junction between the head and center sections of the bed. The bending action of the mattress tends to move or "walk" the mattress off of the support, and also causes the mattress to rub or abrade against the back of the reclined patient. Further, when the adjustable head section of the bed is raised to a sitting position, the mattress compression along the line or axis of the hinges produces a very hard or noncompliant support surface at the lower back area of the patient. The extent or degree of mattress compression is exacerbated as the thickness of the mattress arrangement is increased, because the upper surface of the mattress moves further away from the hinge point of the adjustable bed. Hence, the use of a separate box spring foundation and an overlying mattress for articulated beds has not been achieved with full success, even though such mattress arrangements are quite comfortable and therefore advantageous. In summary, mattress compression in adjustable, hospital-type beds tends to move the mattress from its proper position, rub against the patient's back, ruin the compliance of the mattress at a very critical support area for the patient, and contribute to the development of bed sores, muscular strain, and other deleterious effects which can result in severe patient discomfort.
Another problem associated with articulated hospital-type beds is the safety hazard created by the moving mattress support sections of the bed. It is therefore quite important to locate the hinges, and other moving mechanisms of the bed at a position where the patient will not be able to get his fingers or other appendages inadvertently pinched between the moving parts of the bed.